High-Field 1H-NMR Study of Poly(Vinyl Chloride) Defects

Radical poly(vinyl chlorides), (PVC), obtained in bulk and in suspension polymerizations, and their low molecular weight extracts have been thoroughly studied by high-field NMR to obtain better qualitative and quantitative analyses of their structural defects. Assignments have been achieved by ¹H-¹H decoupling experiments and hyperfine spectral structure analysis of model compounds and low molecular weight extracts. Strong effects of the nature of the solvents used in ¹H-NMR analysis were observed. Most of the defects of these radical PVC's have been quantitatively estimated in terms of average number values in correlation with their Mbar]_n. End-groups of type I'] (= ?CH₂?CHdbnd]CHsbnd]CH₂C1) are about 0.5 per chain; internal double bonds can only be estimated by difference, and their amount increases with increasing conversion. A very low quantity of vinyl chain end I'] (dbnd] sbnd]CHC1sbnd]CHdbnd]CH₂) has been found only in low molecular weight extracts. For the three probable saturated chloromethyl ends II] (dbnd]sbnd]CHClsbnd]CH₂Cl), III] (dbnd] sbnd]CH₂sbnd]CH₂Cl), and IV] (dbnd] >CHsbnd]CH₂C1), only II] and III] were definitely identified. Finally, in taking into account all the endgroups, it has been concluded that branches would be grafted throughout the process. On the average, 4 to 5 branches have been found per chain of high molecular weight PVC.